During the processing of many types of metal and metal coated strips and the subsequent manufacture of products therefrom, it is necessary to apply an electrical potential to the moving strip or to a section thereof for the purpose of heating, charging or testing the strip. As an example, in the manufacture of rolled metallized film capacitors, an electrical potential is applied to a pair of metallized plastic films as the films are wound on a common mandrel for the purposes of monitoring the capacitance of the films during the winding operation. When the monitored value of capacitance reaches a predetermined value, the winding operation is interrupted leaving a capacitor blank with a known capacitance value.
Usually the electrical potential is applied to the films through the agency of a pair of metal rollers over which the metallized surfaces of the films pass in route to the winding mandrel. Heretofore, metallic brushes have been used wherein the brushes are mounted in a holder that is secured to the stationary shaft and biased to move the brush bristles frictionally against either the inner or outer peripheral surface of the roller.
The wear on such a brush device is rapid thus requiring frequent replacement to insure continuing good electrical contact with the roller. When the brushes are mounted within the roller and contact the inner periphery of the roller, the roller must be removed from the shaft to provide the access needed to install a replacement brush. Such an operation is time consuming resulting in significant loss of machine time. Brushes are used to engage the external surface of the roller and considerable area must be provided to insure good electrical contact. Such brushes are usually mounted in holders requiring removal of fasteners before a replacement can be made. Again, with this type of structure, the replacement operation results in considerable down time for the machine.